Project Summary: Stem Cells from the Intervertebral Disc: Do They Vary in Degeneration? Degenerative disc disease and its associated chronic lower back pain is a major U.S. health problem with estimated costs of up to $50 billion yearly. Despite decades of research, a fundamental, multidisciplinary mechanistic understanding of disc degeneration is lacking and, consequently, robust clinical therapies which target the underlying causes rather than the symptoms, are still in the earliest stages of development. In the proposed research program, we focus on the comparison between stem cells (SCs) residing in the nucleus pulposus from healthy and degenerated intervertebral discs. Adults SCs have been known to regulate bone tissue homeostasis and to play an important role in regeneration following injury (i.e. fracture). It was speculated that SCs maintain tissue homeostasis also in tissues with limited regeneration capacity, such as cartilage and the myocardium. Yet it has been shown that during certain pathologies, such as osteoarthritis, osteoporosis and cardiomyopathies, abnormal growth pattern, and changes in differentiation of resident SCs are observed. These changes could attribute to the loss of homeostasis and diminished regeneration process. We have recently shown that SCs do exist in the IVD, even in its degenerated state. There is also some evidence indicating that SCs from other adult tissues might give rise to differentiated nucleus pulposus (NP)-like cells that synthesize and secrete the NP extracellular matrix (ECM). In the proposed study we ask whether the process of disc degeneration affects NP- derived SCs? Our overarching hypothesis is that SCs residing in the degenerated nucleus pulposus demonstrate a change in their number and/or differentiation profile compared to SCs in healthy discs. In order to validate our hypothesis we will pursue the following specific aims: Aim 1. To evaluate the number, proliferation and differentiation potential of SCs from the NP as a function of disc degeneration. Aim 2 To evaluate the differentiation potential of SCs derived from degenerated discs to NP-like cells. The results of this study could provide evidence to a potential role of resident SCs in the process of disc degeneration. Specifically, our findings could be the first step in understanding why resident SCs do not reverse the degenerative process within the disc. Furthermore, the data provided by this study could indicate the route, which future therapies for disc degeneration should take. If indeed NP SCs are found in very low numbers in the disc, exogenous introduction of SCs from other sources could be beneficial for disc regeneration. However, if NP-SCs do maintain some differentiation potential than they might be induced to regenerate the disc by certain genes, proteins or small molecules. PUBLIC HEALTH RELEVANCE: Project Narrative: Stem Cells from the Intervertebral Disc: Do They Vary in Degeneration The proposed study aims to investigate stem cells residing in the nucleus pulposus. It is our hypothesis that stem cells residing in the degenerated nucleus pulposus demonstrate a change in their number and/or differentiation profile compared to SCs in healthy discs.